Explanation

• Acid-base indicators are generally weak organic acids or weak bases.
• They show different colours in acidic and basic solutions.
• For example, phenolphthalein is colourless in acidic solutions and pink in basic solutions.
• Litmus turns red in acidic solutions and blue in basic solutions.

Last verified on 02-11-2026

Explanation

• Molds and yeasts belong to the kingdom Fungi.
• Molds are multicellular fungi that grow as thread-like structures called hyphae.
• Yeasts are mostly unicellular fungi that reproduce mainly by budding.
• Fungi obtain nutrients by absorbing dissolved organic matter from their surroundings.

Last verified on 02-11-2026

Explanation

• The skeleton provides structural support and maintains the body's shape.
• It protects vital internal organs, such as the brain, heart and lungs.
• It helps in movement by providing attachment points for muscles.
• The adult human skeleton consists of 206 bones.

Last verified on 02-11-2026

Explanation

• Chemotropism is the directional growth of a plant or its parts in response to a chemical stimulus.
• The growth of a pollen tube towards the ovule due to chemical signals is an example of positive chemotropism.

Additional information:

• Thigmotropism is a response to touch, hydrotropism to water and phototropism to light.
• Chemotropism helps in plant reproduction, especially during fertilization.

Last verified on 02-11-2026

Explanation

• The axial skeleton forms the central supporting axis of the human body.
• It includes the skull, vertebral column, ribs and sternum.
• The adult human axial skeleton consists of 80 bones.
• The appendicular skeleton consists of the limbs and the shoulder and pelvic girdles, containing 126 bones.

Last verified on 02-11-2026

Explanation

• Nephridiopore is the external opening of the nephridium in an earthworm.
• Nephridia are the excretory organs that remove metabolic waste and help regulate water balance.
• Nephrostome is the funnel-shaped internal opening of a nephridium.
• Earthworms use nephridia to eliminate nitrogenous waste from their bodies.

Last verified on 02-11-2026

Explanation

• Vitamin K is essential for the production of blood-clotting proteins.
• Its deficiency reduces the blood's ability to clot, causing prolonged bleeding.
• It may lead to easy bruising, nosebleeds and excessive bleeding from wounds.
• Vitamin K is found in green leafy vegetables such as spinach, kale and broccoli.

Last verified on 02-11-2026

Explanation

• Vitamin C deficiency → Scurvy
• Causes bleeding gums and poor wound healing.
• Vitamin C is important for collagen formation.
• Main sources: Citrus fruits, guava, tomatoes, and vegetables.

Last verified on 02-11-2026

Explanation

• Malaria is caused by Plasmodium, a protozoan parasite transmitted through the bite of an infected female Anopheles mosquito.
• African sleeping sickness (African trypanosomiasis) is caused by Trypanosoma brucei.
• It is transmitted to humans through the bite of an infected tsetse fly.
• Both diseases are caused by protozoan parasites.

Last verified on 02-11-2026

Explanation

• Sulfur dioxide (SO₂) and nitrogen dioxide (NO₂) react with water and oxygen in the atmosphere to form sulfuric acid and nitric acid.
• These acids mix with rainwater and fall to the Earth as acid rain.
• Carbon dioxide (CO₂) can form weak carbonic acid in rainwater, but it is not considered a major cause of acid rain.

Last verified on 02-11-2026